That was a random scientist, not Magnuson. He told Magnuson what you did to his casserole (if you actually did anything on this playthrough). Magnuson was someplace else. If Magnuson had been there, he would have said something immediately, not twenty years later.
Plus, we don’t know if this is something that Gordon did regularly or not. We don’t know that he only did it right before the cascade, or something he did a week/month before.